Disclosed herein is an environmentally safe paint stripper composition and methods of making and using the paint stripper.
As used herein the term xe2x80x9cDMExe2x80x9d refers to mixtures of dimethyl esters of aliphatic dibasic organic acids, preferably C4-C6 aliphatic dibasic acids, i.e., succinic acid, glutaric acid and adipic acid, respectively. A mixture of such esters is or can be a byproduct of the manufacture of adipic acid and is formed by esterifying a byproduct acid stream with methanol. Although such byproduct mixture of dimethyl esters varies, it is generally about 15 to 30 wt % succinate, about 50 to 73 wt % glutarate and about 6 to 25 wt % adipate. DMEs are available from Solutia Inc., St. Louis, Mo. and E.I. duPont de Nemours and Company, Wilmington, Del. The ratio of dimethyl ester components in a DME mixture can vary from 1-98 parts for each of the three components depending on availability of components. In the following examples, DME-1 is a mixture of about 17-25% dimethyl succinate, 59-73 wt % dimethyl glutarate and 10-14 wt % dimethyl adipate.
As used herein the term xe2x80x9cPVBxe2x80x9d refers to polyvinyl butyral resin, preferably as a dry, free-flowing powder. PVB resin is produced by known aqueous or solvent acetalization processes reacting polyvinyl alcohol (PVOH) with butyraldehyde in the presence of acid catalyst, followed by neutralization of the catalyst, separation, stabilization and drying of the reaction product polymeric resin. PVB useful in this invention can have a degree of acetalization of 0.1-99 mole % acetal, preferably 50-95 mole % acetal, more preferably 70-85 mole % acetal. PVB typically has about 15 to 22 wt % hydroxyl groups calculated as PVOH and up to 10 wt %, preferably 0 to 3 wt %, residual ester groups calculated as polyvinyl ester, e.g. acetate, the balance being acetal, preferably butyraldehyde acetal, but optionally including a minor amount of acetal groups other than butyral, for example 2-ethyl hexanal as disclosed in U.S. Pat. No. 5,137,954. PVB is available from Solutia Inc., St. Louis, Mo. and E.I. duPont de Nemours and Company, Wilmington, Del. In the following examples PVB-1 has a weight average molecular weight (Mw) in the range of 30,000 to 40,000 and about 17.5 wt % PVOH.
European Patent publication EP376687 discloses a paint stripper made with water insoluble organic plasticizers, water soluble organic solvents and polyvinyl formalxe2x80x94a formaldehyde acetal made by reacting PVOH with formaldehyde.
Japanese Patent publication JP52018737 discloses a paint stripper comprising dichloromethane and polyvinyl formal.
German Patent publication DE3235899 discloses a correcting agent for dry removal of inks on a non-absorbing substrate comprising polyvinyl butyral and organic solvents.
Japanese Patent publication JP61223071 discloses a liquid ink eraser comprising polyvinyl butyral and organic solvents.
Solutia Inc.""s Product Bulletin 2149204B discloses Santosol DME solvents in organic-based and water-based formulations for paint strippers and cleaners.
The invention provides paint stripper compositions which can be environmentally safe, i.e. are readily biodegradable. Such paint stripper compositions comprise DME, PVB and water which can be mixed to provide an emulsion. Certain embodiments of the invention also comprise water soluble organic solvents, water-miscible organic solvents, surfactants, emulsifiers, thickeners and/or pigments. The invention further provides a method for removing paint from a substrate by applying the paint stripper compositions of the invention to the painted substrate, and removing the paint from the substrate.